Herbicides and Cover Crops: Problems and Possibilities

Lee BrieseDoctor of Plant HealthCCA, Certified Crop Advisor

@Lee_Briese

It all starts with Goals

• Water management• Wind erosion• Water erosion• Salinity• Diversity

Earth Day 2015

May 2017

“Snirt”

Where to find information?

• USDA Cover Crop Periodic table• Midwest Cover Crop Council selector tool• NDSU weed guide

– Other state weed guides• Use botanical classification

– (cross reference)• Use you knowledge of crops, weeds and

herbicides• Experiment

Cover Crop Chart “Periodic table”

Midwest Cover Crop Council

• NDSU weed guide: rotation restrictions of 4 months or less = safe

• If you follow these recommendations there will not be much time for covers

Herbicide Labels

Herbicide Information

• Weed guides• Herbicide Handbook

Herbicide Selection

• Fit herb to weeds

• Fit cover crop to herb

• Do NOT recommend fitting herb to cover crop

• Benefit vs risk

• Need weed control

• Herbs last for 2-4 weeks of control– Max 6 weeks

Risk Mitigation

• Will have 90% of information needed

• Can have errors• Need to connect the

dots

• Page 107 Herbicide Residue and Fall Cover Crop Establishment

Extension Weed Guide

NDSU Soil Health bottom of page

Better information

Description PagePlant back intervals 6Herbicide site of action 100Herbicide Carryover 102Crop rotation restrictions 104Herbicide residue and cover crops 107Grazing restrictions 110Herbicide efficacy 113Herbicide components 120

• Topramezone + dimethenamid

• Impact + Outlook• 3-9 month restriction

(sugar beet 18)• Short residual ~ 3

weeks– Grasses, most mustards

will be fine– Legumes risky

Armezon Pro

• Clorpyralid + acetochlor + mesotrione

• Stinger + Harness + Callisto

• 10.5-18 months• Long residual 4-6

weeks– Rye, Flax– Maybe barley, wheat,

radish– No legumes,

Resicore

Educated Guess

• Consider weather• Degradation method• Estimate injury

potential• Tolerate some injury

5 “Food Groups” Concept

1. Cool season grasses

2. Cool season broadleaves

3. Warm season grasses

4. Warm season broadleaves

5. Legumes

Gateway cover crops

• Cereal Rye• Radish• Turnip• Oats• Barley

Cereal Rye

• Use to manage excess water• Good weed control

Radish

• Use to reduce water• Reduces compaction• Good frost tolerance• Deep tap root• Fast growth• 1-3#/a

Turnip

• Similar to radish• Better forage• May not winter kill• 1-3#/a

https://www.clarindaherald.com/news/local/cover-crops-cover-chances-of-soil-loss/article_7e70dc6a-feab-11e6-94e5-3766148c46e2.html

Oats

• Less water usage• Better for sandy ground• Good vs wind erosion• Lower frost tolerance• Can control volunteer in

wheat• 30-50#/a

Barley

• Saline tolerant• More frost tolerant

than oats• High herbicide

tolerance• Fast growth• 30-70#/a

Mixes

• Target goals!• Keep it simple• $10-12 for seed• Know how to kill

covers• 30-70#/a good

starting rate– 1 bu grass– 1 # radish

Drill vs broadcast

Cover crop / Herb plot

• Sprayed July 14• Broadcast every 7 days• Not replicated• Water/soil affected

stand• All pics taken Oct 4

1. Huskie2. Callisto3. Resicore4. Spartan5. Engenia6. Armezon Pro7. Sencor8. Dual9. Atrazine10. Select11. Check x2

Covers and Herbicides1. Cereal rye2. Oats3. Barley4. Millet5. Flax6. Buckwheat7. Red clover8. Crimson clover9. Dwarf essex10. Turnip11. Radish12. Kale13. Camelina

1 Day After Treatment/July 15

7 Days/July 21

14 Days/July 29

22 Days/Aug 5

28 Days/Aug 12

35 Days/Aug 19

14 Days After Treatment

1. Huskie2. Callisto3. Resicore4. Spartan5. Engenia6. Armezon Pro7. Sencor8. Dual9. Atrazine10. Select11. Check x2

Covers and Herbicides1. Cereal rye2. Oats3. Barley4. Millet5. Flax6. Buckwheat7. Red clover8. Crimson clover9. Dwarf essex10. Turnip11. Radish12. Kale13. Camelina

Observations

• Lot of rain in 2019• Some injury at 1 day after spraying

– No grass in Select plot– No broadleaves in Armezon Pro or Resicore

• 1-3 species dominated – Was diff at each broadcast timing

• Excess water stress more of problem• Want to test notill vs conv till

Discussion @Lee_Briese